Chapter 8 277 worst-case scenario, as it gives rise to substantially more variability than Caucasian hair. Therefore, throughout this work, conclusions are based on trends, rather than any individual data point. Figure 17. Characteristic lifetimes as a function of repeating stress for Afro hair at 60% relative humidity Figure 18. Characteristic lifetimes as a function of repeating stress for Caucasian hair at differing RH